This disclosure relates to network devices and network communication.
Wireless local area networks (WLANs) are increasingly being used in many different applications, e.g., in home entertainment and business applications.
In one application of a conventional WLAN, one or more wireless clients (e.g., phone, speaker, television, projector, and so on) can be configured to be in communication with a single access point to receive and transmit information.
WLANs generally specify the technologies for wireless communication. Example WLANs can be implemented according to one or more of the following standards: IEEE standards 802.11, 802.11a, 802.11b, 802.11g, 802.11n, 802.16 and 802.20. WLANs typically implement one or more communication protocols in which information is transmitted in packets. Such communication protocols can specify features such as packet size, packet content information, data rates, roaming, and so on. WLANs generally include a communication medium (or transmission channel) that is shared by transmitters (e.g., an access point and one or more wireless clients). To avoid a collision between two transmitted packets on the shared communication medium, a WLAN can implement a CSMA/CA (carrier sense multiple access with collision avoidance) protocol.
FIG. 1 illustrates a timing sequence 100 for transmission of a packet according to a CSMA/CA protocol. When a wireless client wants to transmit a packet (e.g., to an access point), the wireless client first senses (or listens to) the shared communication medium to determine whether the shared communication medium is free (or idle). If the shared communication medium is sensed by the wireless client as being free, the wireless client waits for a DCF (Distributed Coordination Function) interframe space (DIFS), and then transmits a first packet. Otherwise, the wireless client defers access to the shared communication medium until the shared communication medium is free, and the wireless client commences a backoff procedure. The backoff procedure reflects a delay of a number of random timing slots. The random delay occurs during a contention window so that the likelihood of collision between transmitted packets on the shared communication medium is reduced. Thereafter, the wireless client again senses the shared communication medium. If the shared communication medium is free, the wireless client transmits a next packet on the shared communication medium.
Within the CSMA/CA protocol, each wireless client is also operable to send an acknowledgement (ACK) packet each time the wireless client correctly receives a packet. ACK packets are typically sent after a short interframe space (SIFS) as shown in FIG. 1.
In a given WLAN, packet sizes may vary. Therefore, a wireless client that has a large packet to transmit (or receive) may need to occupy the shared communication medium for a longer period of time than another wireless client that has a relatively shorter packet to transmit (or receive).
Unpredictable access to the shared communication medium and delays in transmission of packets may cause problems for a wireless client. For example, information required for providing seamless real time traffic (e.g., audio or video data) is generally much more time sensitive to delays than other non-real time traffic—e.g., if a delay exists in the capture or playback of audio or video data, a user may hear clicks and pops from audio data output or see modulating or jerky video output.